Co-pending applications Ser. No. 554,549, filed Jul. 19, 1990; Ser. No. 554,421, filed Jul. 19, 1990; and Ser. No. 555,307, filed Jul. 20, 1990, which issued Feb 19, 1991, as U.S. Pat. No. 4,993,421, all in the name of the present inventor, describe and claim various aspects of a Cardiovascular Monitoring System in which various physical activities of a subject are monitored along with the emotional state of the subject, and certain ambient conditions are also monitored, to determine what effect, if any, the physical activities and emotional state of the subject have normal and abnormal responses in the subject's EKG.
In the monitoring systems described in the co-pending applications referred to above, the monitored signals relating to the physical activity and emotional state of the subject are recorded in conjunction with the recording of the EKG signals. It is suggested in the co-pending applications that the signals relating to the physical activities and emotional state of the subject may be recorded together with the EKG Signals in a single Holter EKG magnetic tape recorder. In such a case, the latter signals are digitized and multiplexed so that they may be recorded on an unused channel in the Holter recorder. As an alternative, and as also suggested in the co-pending applications, the signals relating to the physical activities and emotional state of the subject may be recorded on a separate recorder. The use of a separate recorder has certain advantages since it enables features of the cardiac monitoring systems of the co-pending applications to be used in other fields such as orthopedics and metabolic studies. An objective of the present invention is to provide such a monitoring system which is particularly constructed for use in such other fields.
Specifically, an objective of the present invention is to provide a musculoskeletal activity monitor (MSAM) in which data of the type derived from some of the various sensors described in the co-pending applications, may be used. While some of the physiological signals used in the monitoring systems of the co-pending applications are used in the present system, emphasis is placed on other aspects of the signals and on their processing and display.
Muscle groups and their essential support bones form an inter-dependent musculoskeletal unit. Muscle function provides force and motion and this is transmitted only by attachment to rigid bones. Bones must have strengths (force carrying capacity) at least equal to those of muscle and other applied forces under all conditions or they will fail-break. Normally, this is the case, for over a period of time, muscle and bone will respond to the usual maximum loads placed upon them by hypertrophy or atrophy, such that their capacity always exceeds the usual maximum stress (force) placed on them. This is visibly obvious in the case of, for example, a sedentary clerk as compared with a body builder or sprinter. Less obvious is the difference in their bones which, however, are just as different in their size and strength as are the muscles they must support, for bones hypertrophy as the muscles but much more slowly. For example, bones respond to changes in loads in months while muscles respond in weeks. A major health problem in this country, and in many other countries, is a literal epidemic of broken bones especially of the lower extremities (legs), and particularly the hip which bears large and unique loads. This epidemic affects primarily the older population, and its effects extend beyond the disability of the fracture, because many other systems are adversely effected by the fracture's disability.
While nutrition and hormones play crucial roles in loss of bone strength, it is now recognized that muscle activity, work and exercise, is also crucial to maintenance of adequate bone strength. It is generally recognized that such activity decreases with age and varies with individuals. However, currently there is no way to measure this, and no way rationally to change such behavior.
It is finally being recognized that muscle force, which may be ten times body weight in running, or three times body weight in walking, and not just "weight bearing" (one-half body weight on one leg), is the crucial force.
Unfortunately, there are no practical means available in the prior art to measure quantitatively the activities that affects bones, especially locomotor activity crucial to maintenance of hip strength. Such a monitor which is needed for research and clinical applications will be described in the ensuing specification.
The parameters needed by both researchers and clinicians in the field of bone loss are number of steps, force of steps, time posture (i.e. lie, sit, erect), changes in posture (these changes exert large forces), and it is desirable to know how the locomotor activity effects the cardiovascular system for the cardiovascular system will ultimately limit maximum locomotor rate add activity level.
In addition, the user of such a system needs information in certain format of importance to him. As noted in U.S. Pat. No. 4,830,021, which issued May 16, 1989, to the present inventor, it is very difficult to make Foot Ground Force (FGF) measurements. However, as described in that patent, a relation exists between vertical acceleration signals (Z) which allows measurement of step rate and a close approximation of FGF. This data plus an EKG signal allows the needs of researchers and clinicians to be met.